Wood-planing machine with angularly disposed cutterheads



Nov. 29, 1955 L. B. CARLSON WOOD-PLANING MACHINE WITH ANGULARLY DISPOSEDCUTTERHEADS Filed Nov. 12, 1954 6 Sheets-Sheet 1 Invenioah Zeuw's B.CaflZsow,

Nov. 29, 1955 L. B. CARLSON WOOD-PLANING MACHINE WITH ANGULARLY DISPOSEDCUTTERHEADS 6 Sheets-Sheet 2 Filed NOV. 12, 1954 Lewis B. CarZsoaw,

M F W =5 I lg 33 Nov. 29, 1955 L. B. CARLSON 2,725,084

WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS Filed Nov. 12,1954 6 Sheets-Sheet 3 12204922202 leazzls B 0112 80032 Nov. 29, 1955 L.B. CARLSON WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS 6Sheets-Sheet 5 Filed Nov. 12, 1954 Lewis .B 0022 80081,

Nov. 29, 1955 B. CARLSON 2,725,084

WOOD-PLANING MACHINE WITH ANGULARLY DISPOSED CUTTERHEADS Filed Nov. 12,1954 6 Sheets-Sheet 6 lawezzior Lewis B. CaHZsow, by 6:07, M; mm, 142,+40% 1 24 ,350

United States Patent WOOD-PLANING MACHINE WlTH ANGULARLY DISPOSEDCUTTERHEADS Lewis B. Carlson, Milton, Mass, assignor to S. A. WoodsMachine Company, Boston, Mass, a corporation of MassachusettsApplication November 12, 1954, Serial No. 468,347 7 lairns. (Cl.144-116) This invention relates to wood planing machines of the type inwhich rotary knife-carrying heads operate on rough boards which areadvanced transversely thereto. When such a machine operates on one orboth of the wide faces of the board only, it is commonly referred to asa surfacer and there are top surfacers, bottom surfacers and doublesurfacers. While the word planer may. have a generic significance it isusually used specifically to apply to a machine in which both faces ofthe board are planed and which also embodies sideheads for operating onthe edges of the board. When such sideheads cut a tongue on one edge anda groove on the other, the machine is specifically termed a matcher. Inany case additional heads, whether horizontal or vertical, may be alsoprovided to make a hogging out before the final planing cut, and aplaner frequently has attached thereto a profiler, so-called, to give acontour to the work as it emerges from the planing heads proper. In theaccompanying drawings a planer in the specific sense of that Word isillustrated and the description will correspond, but the application ofthe invention is not limited to this specific type of machine.

characteristically, in these planing machines rough boards are forwardedalong a lateral guide or fence by feed rolls, past the cutting heads,one following another. Feeding-out rolls are provided beyond the cuttingheads. When the boards are long, as is the usual case in soft woods,they will span the space between the heads so that a board will beengaged by the feeding-out rolls before leaving the feeding-in rolls. Inthe case of short pieces, one board pushes the one ahead. The practiceis to so operate the machine that the boards of whatever length are notonly in end-to-end succession, but in end abutting relation, this beingpartly from the desire to avoid clipping as hereinafter referred to.Thus the boards are fed to the feeding-in rolls, for instance, by a feedtable tending to feed them somewhat faster than feed rolls do, so thatthe ends are abutted and, to a certain extent, interlocked one withanother to prevent the ends moving out of the common plane.

The object of the invention is to provide a new organization of such amachine which will facilitate its work, in particular avoidingdifiiculties which arise with the usual planer because of insufficientcontrol of the position of the board being operated on, particularly atthe ends thereof, with effects known as clipping, disfiguring the end,and requiring that a portion of the board be cut off and discarded.

The cause of this clipping effect may be explained as follows. Thestream of boards is forwarded, in endabutting relation, past thecutterheads along a horizontal supporting surface or bed, and varioushold-down means are provided for keeping the boards flaton this bed. Inparticular, at the intake side of the top cutterhead this takes the formof a chipbreaker shoe which is mounted for vertical movement toaccommodate varying thicknesses of the boards. The edge of the shoeextends parallel to the axis of the cutterhead and its rearward face isusually contoured to approximate the cutting circle in order to maintaincontrol of the board as long as possible. However, there is an intervalwhere the trailing edge of the forward board and the leading edge of thesucceeding board pass out from under the chipbreaker shoe but have notarrived at the knives of the cutterhead. If the board Patented Nov. 29,1955 is somewhat crooked or has been distorted by the latter hold-downmeans of the machine sothat it is under considerable strain, thetrailing edge of the forward board may spring upwardly or the leadingedge of the succeeding board may similarly move upwardly and thecutterhead will cut diagonally to the face of the board, making a taperor bevel at that end. This is known as clipping and, since boards arecut in standard lengths of feet a considerable portion of the board maybe wasted when it is trimmed off to a shorter length. The end-lockprovided by the forcible butting together of the ends of the boardsresists the movement upwardly of one or both of the ends but, whiledoubtless improving the situation as regards clipping, is not effectiveto prevent it entirely.

To one casually examining the drawings which accompany this application,it will appear that a salient feature of the machine shown is thedisposition of the horizontal cutterhead at an angle to the liner feedof the machine, and indeed with proper correlation with other featuresthis provides for the improved results to be obtained.

- It would be misleading and incorrect, however, to suggest that theinvention consists solely in such a disposition of the top head orcylinder. It is the fact that h skew cut or draw cut across the board iseffected, but this is not claimed as novel in itself. Joiners handplanes with the throat and the edge of the plane iron disposeddiagonally to the length of the sole, have long been known and aretermed skew planes. It would be natural then, when a planing mechanismwith a rotary cutterhead was introduced, to suggest that the knivesmight be similarly placed on the skew relative to the direction ofmotion relative to the work. The only commercial application of this ofwhich I know was the provision, seventy-five years or more ago, ofmachines for taking a light finishing cut on previously assembled doorframes. These machines had a work table over which single door frameswere advanced by hand, above which table was a rotary cutterhead placedat an angle. The door frames, of course, were not assembled from roughlumber but from finished lumber, and this cut was a final smoothingoperation after the rails and stiles had been assembled. It is clearthat if we have an assembled door and plane it along the length of thevertical stiles we are working with the grain in the customary preferredmanner of planing. As the end of our door finally passes out from underthe head however, it encounters the rail, the grain of which extendstransversely to that of the stiles. Therefore the cutterhead knife, ifparallel to the grain in the rail, is likely to knock off the trailingedge. The'diagonal disposition of the cutterhead, Whether or not anadvantage in planing the stiles, distributed the splitting strain on therails to make such damage less likely. I believe that these machines areobsolete, the corresponding operation now being performed by sandingmachines. I believe, furthermore, that the diagonal disposition of thehead has not hitherto found any application in planers in which the cutswere along the grain of successive boards, the trailing end of eachbeing engaged by a succeeding one.

In present day planers the speeds of feed are very great, beingspecified in hundreds of feet per minute. The heads also rotate at veryhigh speeds and the aggregate relative speed of the work and the knifeis great. In general this is an advantage in cutting, but the out has togo where the parts are moving and, as explained, this causes difiicultyat the ends of the boards which is minimized by the presentconstruction.

With this introduction I may proceed to the detailed description of theillustrative embodiment of my invention, shown by way of example in theaccompanying drawings whereir1 Figure 1 is a simplified and diagrammaticplan, of the type known to manufacturers as a floor plan or foundationplan, intended merely to give an overall view of the principal elementsof the machine within the restricted scope of a patent drawing;

Fig. ,2 is a corresponding side elevation;

Fig. 3 is a fragmentary longitudinal section in a vertical plane showingthe top and bottom cutterheads and mechanism cooperating more directlytherewith;

Fig. 4'is a corresponding plan view;

Fig. 5 is a transverse section as seen from the right of Figs. 3 and 4.The reader is looking in the direction of feed at the rear side of thechipbreaker which precedes the top head;

Figure 6 is a side elevation of that chipbreaker and its mounting asseen from the front side, so-called, the left side as one looks forwardin the direction of feed;

Fig. 7 is a corresponding fragmentary plan;

Fig. 8 is a vertical section of the chipbreaker showing its constructionand mounting at the other, or guide side;

Fig. 9 is a corresponding fragmentary plan; and

Fig. 10 is a diagrammatic section and Fig. 11 is a diagrammatic plan toaid in the description of certain features of operation.

All figures have been simplified by omitting or breaking away variousparts which would appear in a complete machine, including details ofmounting and drive, shavings disposal and so on which would be wellunderstood by one skilled in the art and the illustration of which wouldonly complicate the drawings and obscure the important features ofconstruction and correlation.

The travel of the stock is from right to left in the figures and unlessthe context otherwise indicates forward means in the direction oftravel, rearward means toward the feeding-in end and in advance of meansnearer the feeding-in end.

Referring to Figs. 1 and 2, the boards are fed in at the right, as bymeans of a feed table, so-called, over a bed 10 which, in cooperationwith other physically separate parts, provides a horizontal supportthroughout the length of the machine, except where it is interrupted topermit the bottom head to operate. They are taken by two pairs of feedrolls 12, 12, the off edge of the board is guided by a guide or fence14, shown in Fig. l by a single dot-and-dash line. The feed rolls 12advance the boards in a continuous series in end-to-end relation pastseveral cutterheads, the boards moving first beneath the chipbreakershoe 16, not shown in Figs. 1 and 2 but mounted on the standards 18(Fig. 2) (which also carry in the usual manner the top head yoke, notshown) then, in

succession, under the top head 20, over the bottom head 22 whichoperates in a gap in the bed and, when four sides of the board are to beplaned, between the sideheads 24, which may form part of a matcherworks. The board B is then taken by feeding-out rolls 26 to con tinueits movement toward the left. In Fig. 1 the motors shown at 28 at theleft are for the cylinders 29 of a profiling attachment which areindicated in Fig. 2, such an attachment being a common adjunct inmachines of this type, but the presence or absence of which is'of nosignificance as regards the present invention.

The cutterheads and 22 are of any usual or suitable type utilizingknives which extend lengthwise in positions corresponding to elements ofa cylindrical surface and rotating so that the knife in making the cutmoves generally in the opposite direction to the travel of the board.

As appears clearly in Fig. l, the axes of the top and bottom heads 20and 22 are inclined to the longitudinal line of themachine, making anacute angle with the guide 14 as measured at the right of the figure,the angle illustrated being about 65 Coming now to Fig. 3 it may benoted that for clearness the cutterheads are shown as circles and theadjacent parts of chipbreaker shoe 16 to correspond. The sectioningplane as regards these parts might be considered as inclined at theangle of 65 to the longitudinal center line of the machine. Other partshowever are shown as if the section were by a plane parallel to thelongitudinal line. In other words the eccentricity of diagonallydisposed parts which theoretically should appear in a section by thelatter plane and which would show,.for example, the cutterheads asellipses with parts at the further side in elevation, has beensuppressed. This will not be misleading in view of Fig. 4.

As seen in Fig. 3 the board B advances over the platen 30 (which is ineffect a continuation of bed 19) and which may be adjusted alongdiagonal ways 32 in customary manner, and is yieldably held thereagainstby the chipbreaker shoe 16 movably mounted in a manner to be describedon lateral cheek pieces 34 which extend bracketlike from the standards18 at either side of the machine. Herein the chipbreaker is in one pieceacross the width of the machine. A sectional chipbreaker would in elfectbe several shorter chipbreaker shoes in alignment and utilizingintermediate supporting means.

The name chipbreaker shoe chances to be suggestive of the crosssectional shape of the part 16 as illustrated. It has an extended toeportion 36 which is parallel to the axis of the head and extends asclosely to the bottom line of the head as is possible consistently withclearing the cutting circle of the knives. It carries a facing or top'lift 37 which as seen in Fig. 5 may be formed in sections, and itsrearward face 38 (the vamp of the shoe) is curved to correspond to thecutting circle. The shoe is movably mounted to permit it to accommodateitself to the varying thicknesses of the work, and the pressure exertedthereby may be controlled by springs. Herein compression springs 40increase the pressure due to its weight. As a homely simile we mightcompare the shoe with the pushing blade of a snow plow rigged diagonallyat the front of a truck. In the present case the relative arrangement ofthe cutterhead and chipbreaker and a mounting of the latter whichpermits it to maintain close approximation to the cutterhead at alltimes is of great importance.

It is clear that the chipbreaker cannot, when approximating closely tothe lower right quadrant of the cutting circle, merely move verticallywithout interfering with the same. If it retreats too far it will notbreak the chip and the board may be split instead of cut. It isdesirable that it move on simple rotating bearings for ease and rapidityof motion. If it were pivoted to swing about an external axis parallelto that of the cutterhead it would not respond properly to thelongitudinally mov ing boards. On the other hand if the axis weretransverse to the machine, perpendicular to the guide, the toe of thechipbreaker would not maintain its parallelism to the cutterhead axisand would not bear uniformly on the work.

In the example of the invention shown the chipbreaker shoe 16 issupported from the cheeks 34 for movement bodily in a plane longitudinalof the machine under the control of linkwork which gives a compoundmovement to the toe portion 36 which remains always parallel to thecutterhead axis but moves upwardly and rearwardly in a path closelyapproximating the adjacent are of the cutting circle.

In the construction shown, the chipbreaker shoe as a unit receiveslateral support from the cheek pieces 34 while moving freely betweenthem. As best seen in Figs. 4 and 5, the chipbreaker embodies in itsconstruction two side members 42 supporting the sole and the curved face38. As seen in Fig. 4, the nigh member 42 (lower in the figure) liesdirectly against the nigh cheek piece 34 at the .lower portion of thefigure, and they are provided with finished surfaces where they contactat the plane X, so that they may slide freely over one another in themovement of the chipbreaker shoe. In the off side, the upper portionviewing Fig. 4, the part 42 is spaced from the adjacent cheek piece 34so that there is provided on that side of the chipbreaker shoe anextension 43 which has a finished surface cooperating with the finishedsurface of the cheek piece 34 in the plane Y.

Referring now to Fig. 3 and also Figs. 69, the chipbreaker shoe ismounted for movement between the guiding surfaces thus described bymeans of pivoted links extending between the cheek pieces 34 and thesides 42 and properly correlated to give the desired motion. In thepresent instance, these links are parallel links defining, with the lineof centers on the cheek pieces 34 and the line of centers on thechipbreaker sides 42, a parallelogram the obliquity of which alters asthe parts move and the parallelograms, while alike in dimension, aredifferentially positioned as indicated by the contrast between Figs. 6and 7 showing the nigh side of the machine, and Figs. 8 and 9 showingthe off side.

Referring now to these figures, in Fig. 6 I have shown an upper link44-n joining the center a on the chipbreaker to the center b on thecheek 34, and a lower link 46-11 joining the center c on the cheek pieceto the center d on the chipbreaker.

Referring now to Fig. 8, on the off side an upper link 440 joins centerm on the chipbreaker to center 11 on the cheek piece 34, and a lowerlink 46-0 joins center 0 on the cheek-piece to center p on thechipbreaker. The rectangles abca' and mnop are at all times similar inthe geometrical sense but they are not in transverse alignment therespective vertices of the latter being displaced longitudinally of themachine farther to the front to correspond with the obliquity of thecutterhead axis and of the toe portion 36 of the chipbreaker. The axesof the bearings and pivot pins at these points, however, areperpendicular to the longitudinal plane of the machine. Thus, if we lookat Figs. 6 and 8, and imagine the links to swing clockwise, the toe ofthe chipbreaker in Fig. 6 will move in a predetermined directionrelative to the cutting circle of the head 20, adjacent thereto.Likewise the toe in Fig. 8 will move in the same manner relative to thecutting circle of the head adjacent thereto, and this will be true allacross the diagonal width of the cutterhead, the position of the toe 34and the face 38 relative to the cutterhead and its cutting circle beingthe same throughout the width of the chipbreaker shoe.

As is seen in the drawings, the lines b-c and m-0 between the fixedcenters incline upwardly slightly away from the cutterhead and the linesa-p and m p will move parallel thereto. The lines between the pairs ofcenters a-p, m-n, d--c, p0, may also incline slightly upwardly andforwardly, or to the left in the figures. The parallelograms are obliqueand when the chipbreaker responds to the pressure of the board with anupward movement the partial collapse of the parallelograms will be suchthat the toe of the chipbreaker will move with a compound movementupward and also slightly to the rear in a path closely approximating thecutting circle of head 40 which is the desired efiect.

At the feeding-out side of the cutterhead 20 the board is held down byan adjustable hold-down 48, the lefthand edge of which, viewing Fig. 3,is close to the cutting circle of the cutterhead 20, opposing theright-hand end of platen 30, and which extends across the gap in the bedthrough which the lower cutterhead 22 operates and opposes the platen 50at the forward or feeding-out side or" the lower cutterhead 22,. Thehold-down 48 may be of any suitable or conventional construction, exceptthat its rearward edge is disposed diagonally to correspond with theinclination of the cutterhead 26. The board then passes, still undercontrol of the guide 14, between the sideheads 24 if such are present.The chipbreakers and hold-downs which cooperate with the sideheads maybe of conventional form and are not illustrated.

Fig. 4 illustrates the diagonal disposition of the cutterheads 20 and 22relative to guide 14. It will be clear that when the cutterheads rotatecounterclockwise viewing Fig. 3 then, because of the diagonaldisposition of the knives a component of force will be set up tending todiminish friction.

keep the board pressed against the guide or fence 14, which is smoothlyfinished and may be chrome plated to This pressure is a decidedadvantage because good work depends on accurate control and positioningof the boards and the guide line is one of the fixed points from whichwe work. Since a component of the thrust of the knives is directed tothe guide a lesser pressure of the feed rolls will be effective to feedthe work. This is desirable because excessive pressure is likely toloosen knots. Also excessive pressure may crush the fiber of the woodand poorly planed surfaces will result. The obliquity of the heads, whenutilized in connection with such guide, is of particular importance whensideheads 24 are utilized and insures their proper and economicalaction, the off head 24, or upper head viewing Fig. 1, being set up tocut just inside of the line of the guide and the nigh head 24 beingproperly spaced therefrom.

Referring now to Figs. 10 and 11, the importance of the diagonaldisposition of the cutterhead when used in correlation with a guide andproperly acting hold-down as described in preventing clipping will nowbe explained. In Fig. 11 the chipbreaker shoe 16 and the hold-down 48are diagrammatically shown, the numerals being placed in quotation marksto indicate the diagrammatic character of the representation. There is adefinite space between their opposed edges to permit the top cutterhead20 to work, as will be apparent from Fig. 10. The edge or" the knifeactually moves through the board for a slight distance at opposite sidesof its lowermost point along the dot-and-dash line L in Fig. 11. This iswhere the knife acts and this is where the board is out. Whatever partof the board is there gets cut. If the end of the board is sticking upinto the air the knife digs in and chops the top edge off or, withnothing to break the chip, splits it oil? for an even greater distance.Now I have shown in Fig. 11 between the parts 16 and 48 the abuttingends of two successive boards B. Where the cutterheads and thehold-downs are arranged in conventional manner at rightangles to thelength of the machine, the parts of the boards in this space areunsupported throughout their width. But in the construction shown theupper portion of the trailing end of the leading board has not passedout from under shoe 16 and the upper portion of the end of the followingboard is also beneath it. Indeed, in the case of a board wider than thedistance between the edges of 16 and 48 measured perpendicular to thecenter line the end edge of the board could never be free of at leastone of the holddowns. In general, looking at the right-hand or followingboard in Fig. 11 its lower left-hand corner emerges from under shoe 16and advances to the cutting line L. The knives first engage the cornerand at this time the projecting portion is held down along the diagonalwhich at its upper end is at the extreme end of the board. Throughout asubstantial part of its width the board is still under the shoe. The cutprogresses parallel to the diagonal under generally similar conditions.As the board passes the head the lower right-hand corner of its trailingend first moves free of the shoe 16 but the upper right-hand corner isstill held. As the cut proceeds diagonally upward in the figure acrossthe end portion of the board conditions are similar until the cut isalmost completed.

If we turn Fig. 3 upside down, we will see that, at least schematically,it would represent a planer in which the bottom head came first, theboards moving over a bed 36 at their upper side, and along a guide 14.In practice planers are not usually constructed in that manner.Moreover, if we consider the head 20 alone, its position would thencorrespond to that of the cutterhead of a so-called bottom surfacer (asit corresponds to the head of a top surfacer in the right sideposition), and if the shoe 16 were supported in such manner as to pressthe board against the overhanging bed 30, the operation of the partswould be the same. The details of mechanical construction of such amachine doubtless would be quite different in practice. For instance,the guide would ordinarily be at the other side and, since gravitywouldbe acting to move-the shoe 16 'away'fromthe work 'instead of toward thesame, the shoe would have to be supported or counterbalanced as'byincreasing the power of the springs 40, or otherwise. It is not to beexpected that a design for a given construction would be exactlysuitable for a reversed construction, but the general operation of theparts and the means provided for giving them the proper motions would begenerally similar and the machine operate in accordance with the sameprinciples.

I amaware that the invention may be embodied in other specific'formswithout departing'from the spirit or essential attributes thereof, and Itherefore desire the present embodiment to be considered in all respectsas illustrative and not restrictive, as is in fact clear in severalmatters from the description itself. Reference is to be had to theappended claims to indicate those principles of-the inventionexemplified-by the particular embodiment described and which I desire tosecure by Letters Patent.

1 claim:

l. A wood-planing machine of the type in which a succession of boards inend-to-end relation are advanced by feeding means over a bed and along alateral guide into cooperation with the planing means, said planingmeans comprising at least one rotary cutterhead, having knives the edgesof which correspond to elements of a cylinder, said head being driven tomove the knives through the boards in a direction opposing the directionof feed, the axis of the head being inclined at a substantially acuteangle to the guide measured on the side in advance of the cutterhead,and hold-down means comprising a pressure device for bearing on the workimmediately in advance of the cutterheadand having an angularlyextending work-engaging surface extending parallel to the axis of thehead closely adjacent the cutting circle thereof, a supporting frameworkfor said device and means for connecting the device to said frame workto provide for yielding movement of said surface along a pathapproximating the adjacent arc of said cutting circle comprisinglinkwork connected to said device by pivots extending substantiallyperpendicular to the direction of work feed and by parallel pivots tothe framework.

2. A wood-planing machine of the type in which a succession of boards inend-to-end relation are advanced byfeeding means over a bed and along alateral guide intov cooperation with the planing means, said planingmeans comprising at least one rotary cutterhead, having knives the edgesof which correspond to elements of a cylinder, said head being driven tomove the knives through the boards in a direction opposing the directionof feed, the axis of the head being inclined at a substantially acuteangle to the guide measured on the side in advance of the cutterhead, apair of checks in advance of said head at either side thereof havinginteriorly directed smooth guiding surfaces disposed in vertical planessubstantially parallel to the line of work feed, a pressure devicereceived between them having cooperating smooth surfaces for guidedmovement between the first-mentioned ones, said device having awork-engaging surface extending parallel to the axis of the head closelyadjacent the cutting circle thereof and means for supporting the devicefor a guided movement between said cheeks wherein said surfacethroughout its. length moves in a path corresponding closely to theadjacent arc of the cutting circle.

3. A wood-planing machine of the type in which a succession of boards inend-to-end relation are advanced by feeding means over a bed and along alateral guide into cooperation with the planing means, said planingmeans comprising at least a rotary top cutterhead, having knives, theedges of which correspond to elements of a cylinder, said head beingdriven to move the knives through the boards in a direction opposing thedirection of feed, the axis of the head being inclined at asubstantially acute angle to the guide measured on the side in advanceof the cutterhead, a pair of cheeks in advance of said head ateitherside thereof, a pressure device in advance of the head having awork-engaging surface extending parallel to the axis of the head closelyadjacent the cutting circle thereof and means for supporting the devicefrom said cheeks for a movement wherein said surface moves throughparallel positions inv a path 'corresponding closely to the adjacent arcof the cutting circle said means comprising upper and lower links oneach side, the pivotal centers of said links on one side being offsetlongitudinally relatively to those on the other side in such manner thatthe connecting lines between their homologous center points are parallelto the axis of the head.

4. A wood-planing machine as set forth in claim 3 wherein the links ateither side form the ends of a'parallelogram, and the line between thecenters on either cheek inclines ina vertical direction away from thebed and also rearwardly.

5. A wood-planing machine as set forth in claim 3 wherein the links ateither side form the ends of a parallelogram, and the line between thecenters of each link inclines in a vertical direction toward the 'bedand also forwardly.

6. A wood-planing machine having a bed and a lateral guide along oneside thereof,feeding means for'forwarding boards in end-to-endsuccession'over said bed and along the guide, a rotary cutterhead at oneside of the bed the bed having knives disposed to correspond to elementsof a cylinder and having its axis inclined at an acute angle to theguide measured on the side in advance of the cutterhead, said headrotating to carry the knives into the boards in a direction opposite tothat-of the feed, a board hold-down in advance of and one succeedingsaid cutterhead having inclined edge portions parallel to the axis ofthe head and extending into close proximity to the cutting circlethereof, and means foryieldably mounting the first-mentioned hold-downto provide for movement of its said edge portion through a path closelyapproximating the adjacent arc of said cutting circle.

7. A planer having a bed and a lateral guide along one side thereof,feeding means for'forwarding over said bed and along said guide, aseries of boards in end-abutting relation, a first top and second bottomrotary cutterhead each having knives disposed to correspond to elementsof a cylinder and having their axes inclined at an acute angle to theguide measured on the side in advance of the cutterhead, said headsrotating to carry the knives into the boards in a direction opposite tothat of the feed, holddown devices in advance of the first head, betweenthe two and following the bottom head presenting inclined work-engagingedge portions parallel to the axes of the heads and extending into closeproximity to the adjacent cutting circles thereof and a side cutterheadfollowing the other heads having its cutting circle projecting inwardlypast the line of the guide for operating on the edge of the board whichis pressed against the guide by the action of the top and bottom heads.

References Cited in the file of this patent UNITED STATES PATENTS 4,283Andrews Nov. 21, 1845 201,624 Norris Mar. 26, 1878 298,454 Eldredge May13, 1884 390,829 Welch Oct. 9, 1888 452,632 Bennett May 19, 18911,292,579 Clement et al. Jan. 28, 1919 2,102,186 Nicholson et al. Dec.14, 1937 2,312,439 Peterson Mar. 2, 1943 FOREIGN PATENTS 616,952 GermanyAug. 9, 1935

